1. Field of the Invention
The present invention relates to technology of a flat panel display and more particularly to a liquid crystal display device to display image data inputted from external devices and a method for transferring the image data inputted from external devices to a displaying means.
2. Description of the Related Art
FIG. 9 is a schematic block diagram explaining functions of a conventional liquid crystal display device; FIG. 10 is a schematic circuit diagram showing one form of connections of each of source drivers of the conventional liquid crystal display device of FIG. 9; FIG. 11 is a timing chart explaining operations of the liquid display device of FIG. 9; and FIG. 12 is a view showing a form of wiring to a source driver in the conventional liquid crystal device in FIG. 9.
In a conventional liquid crystal display device as shown in FIG. 9, as wiring between a signal processing circuit and source drivers, a bus line is provided which has the number of bits being two times larger than that of image data inputted from external devices or being an integral multiple of the same. That is, in the past when the number of bits of image data inputted from external devices was as small as 4 or 6 and a source driver with multiple pins for outputting was not available and therefore many source drivers were required, it was necessary to provide such bus lines to which source drivers were connected.
Japanese Laid-open Patent Application No. Hei 6-45508 discloses such a display device as has configurations described above (hereafter as a xe2x80x9cfirst conventional display devicexe2x80x9d). The first conventional display device is comprised of a board, two or more semiconductor driving circuits mounted on the board, two or more first bonding pads used to feed a clock signal to the semiconductor driving circuits, which are disposed in the vicinity of each of the semiconductor driving circuits on the board, two or more second bonding pads used to feed a data signal to the semiconductor driving circuits, which are disposed in the vicinity of each of the semiconductor driving circuits on the board, two or more clock signal lines disposed on the board and connected to the first bonding pads and two or more data signal lines disposed on the board and connected to the second bonding pads. Two or more data signal lines may contain both a first line to connect the second bonding pads to each other and a second line to feed the data signal to the first line, or may be connected to each of the first bonding pads.
The semiconductor driving circuits may be comprised of a discrete semiconductor device such as a transistor or a discrete semiconductor component, or of integrated circuits (IC) into which many semiconductors are integrated. In the first conventional display device, since the clock signal can be fed separately to the semiconductor driving circuits through the clock signal line and the first bonding pad, by supplying the clock signal with staggered timing for every semiconductor driving circuit, a data signal can be fed independently to each of the semiconductor driving circuits. Unlike in the case of a fluorescent display panel, bonding pads and signal lines used to output a data signal are not required, thus allowing the reduction in the number of bonding pads. As a result, the wiring density around the driving circuits can be reduced. It is also reported in the description of the disclosed display device that, since adequate distance between the driving circuit and the bonding pad can be maintained owing to the reduction in the wiring density, the reliability required when they are wire-bonded is more improved compared with the conventional fluorescent display panel.
Japanese Laid-open Patent Application No. Hei6-148665 discloses another example of a conventional display device (hereafter as a xe2x80x9csecond conventional display devicexe2x80x9d). The second conventional display device is provided with two or more driving circuit devices mounted on a glass board, groups of wiring for inputting and outputting to and from these driving circuit devices and terminal areas for inputting from external devices. The wiring groups for inputting provided at the inputting terminal areas are divided into two groups, one to be used in common by the driving circuit devices and the other to be used independently by each of the driving circuit devices. In the second conventional display device, though impedance of the inputting wiring has an influence on displaying characteristics of the liquid crystal device, it does not mean that all wiring is affected equally and the degree of the influence varies depending on the use of the wiring. The wiring group being affected little by the impedance is separated from that being much affected by the same. The wiring group being affected little is so configured that power is supplied through a bus line from one terminal for external input to each of driving circuit devices and the wiring group being affected much is so configured that power is supplied independently to each of driving circuit devices. The use of the wiring designed specifically for the wiring group being affected much allows the impedance to be lowered and excellent display characteristics to be obtained. In addition, the wiring group being affected little is connected by the bus line, thus preventing the number of input terminal areas being increased.
However, in recent years when the number of bits of image data and the transfer speed of the image data are increased, since a transfer frequency of the bus line and operational frequency of the source driver in the first and second conventional display devices have their own upper limit, it is necessary that the number of bits of the bus line be an integral multiple of that of the image data. This causes increased area occupied by wiring on the printed board and increased number of the lines for wiring, thus inducing increased noise influences due to EMI (electromagnetic interference).
In view of the above, it is an object of the present invention to provide a liquid crystal display device and a method for transferring image data wherein the length of wiring connected between a signal processing circuit and each of source drivers can be reduced and EMI caused by through holes can be prevented, thus improving anti-electromagnetic interference characteristics.
According to a first aspect of the present invention, there is provided a liquid crystal display device for displaying image data inputted from external devices comprising:
a means to split one display line of the image data in accordance with the number of source drivers used to drive a displaying means;
a means to read, in serial, each of the split blocks of the image data and to transform the read image data in unit of dots into image data in serial form;
a means to transfer, in serial, the image data transformed to serial form, with each of the split blocks of the image data being associated with each of the source drivers in a one-to-one state;
a means to transform the image data in serial form serially transferred to each of the source drivers to image data having a specified bit length in parallel form and to produce it;
a means to combine the image data in parallel form transferred from each of the source drivers in accordance with the arrangement of the source drivers and to restore one display line of the image data; and
a means to transfer, in parallel, one display line of the restored image data to the displaying means to display it.
According to a second aspect of the present invention, there is provided a liquid crystal display device for displaying image data inputted from external devices comprising:
a signal processing circuit to split one display line of the image data in accordance with the number of source drivers used to drive a displaying means, to transform each of the split blocks of the image data to image data in serial form, and transfer, in serial, the image data transformed to serial form, with each of the split blocks of the image data being associated with each of the source drivers in a one-to-one state;
whereby the above two or more source drivers are connected, in parallel, to the signal processing circuit and transform the image data in serial form transferred in serial thereto to image data having a specified bit length in parallel form and produce it; and the displaying means restores one display line of the image data by combining the image data in parallel form transferred from each of the source drivers in accordance with the arrangement of the source drivers and displays one display line of the restored image data transferred in parallel thereto.
In the foregoing, a preferable mode is one wherein the signal processing circuit has two or more line memories used to split one display line of the image data into the number of blocks of the image data in accordance with the number of source drivers used to drive the displaying means.
Also, a preferable mode is one wherein the signal processing circuit has a serial transforming circuit provided in a state of being associated with each of the split blocks of the image data in a one-to-one relationship, which is used to transform each of the split blocks of the image data stored in each of the line memories to the image data in serial form in a state of being associated with each of the split blocks of the image data.
Also, a preferable mode is one wherein the serial transforming circuit transfers, in serial, the image data transformed to serial form with each of the split blocks of the image data being associated with each of the source drivers in a one-to-one state.
Furthermore, a preferable mode is one wherein each of the source drivers has a parallel transforming circuit connected to the serial transforming circuit in a one-to-one state and which is used to transform the image data transferred in serial to each of the source drivers to image data having a specified bit length in parallel form and to produce it.
According to a third aspect of the present invention, there is provided a method for transferring image data inputted from external devices to a displaying means comprising steps of:
splitting one display line of the image data in accordance with the number of source drivers used to drive the displaying means;
transforming each of the split blocks of the image data into image data in parallel form;
transferring the image data transformed to serial form with each of the split blocks of the image data being associated with each of the source drivers in a one-to-one state;
transforming the image data in serial form transferred in serial to each of the source drivers into image data having a specified bit length in parallel form to produce it;
restoring one display line of the image data by combining the image data in parallel form produced in previous steps in accordance with the arrangement of the source drivers; and
transferring, in parallel, one display line of the restored image data to the displaying means.
According to a fourth aspect of the present invention, there is provided a method for transferring image data inputted from external devices to a displaying means comprising steps of:
processing signals to split one display line of the image data in accordance with the number of source drivers used to drive the displaying device, to transform each of the split blocks of the image data into image data in serial form and to transfer, in serial, image data transformed into serial form with each of the split blocks of the image data being associated with each of source drivers in a one-to-one state;
transforming, through the use of the source drivers, the image data in serial form transferred in serial to each of source drivers into image data having a specified bit length in parallel form to produce it;
restoring one display line of the image data by combining the image data in parallel form transferred from the source drivers in accordance with the arrangement of the source drivers; and
displaying one display line of the restored image data transferred in parallel to the displaying means.
In the foregoing, it is preferable that the above step of processing signals contains a step of splitting one display line of the image data in accordance with the number of the source drivers used to drive the displaying means and of storing the split image data into a memory.
Also, it is preferable that the above step of processing signals includes a step of transforming each of the split blocks of the image data stored by the storing steps, with each of storing processes being associated with each of the split blocks of the image data in a one-to-one state, to image data in serial form with each of transforming processes being associated with each of the split blocks of the image data.
Also, it is preferable that the above step of transforming the image data includes a step of transferring, in serial, the image data transformed into serial form with each of the split blocks of the image data being associated with each of the source drivers in a one-to-one state.
Furthermore, it is preferable that the above step of transforming through the use of the source drivers includes a step of transforming the image data into serial form transferred in serial, to each of source drivers, with each of the serial transforming steps being associated with each of transferring processes in a one-to-one state, to image data having a specified bit length in parallel form to produce it.